1. Field of the Invention
The present invention relates to a compass, wherein a magnetic sensor derives azimuthal data from the geomagnetism it detects, and an azimuth determined on the basis of the azimuthal data is optically displayed.
2. Description of the Related Art
As a device for determining an azimuth, a magnetic compass is well known. This magnetic compass comprises a magnetic needle which is free to pivot and which moves in response to the geomagnetism until its one end points to the geomagnetic North Pole. An electronic compass is also well known. This electronic compass comprises a pair of magnetic sensors which are formed by magnetic resistor elements, Hall elements, or the like and are arranged perpendicular to each other. Each magnetic sensor produces a voltage in response to the geomagnetism it detects, and on the basis of this voltage, a geographic direction is determined and displayed on a display device.
With the above magnetic compass and electronic compass, however, it is impossible to know the true "north" direction since the azimuth determined by the conventional compasses is based on the data indicating the geomagnetic North Pole. In other words, the above compasses are merely useful in roughly determining the north direction. It should be noted that the relationships between the true south-to-north direction and the direction of the geomagnetism differs, depending upon geographic locations on the globe. In order to know the true azimuth, therefore, an azimuth based on the geomagnetism has to be first determined by use of the above compasses, and then the azimuth, thus determined, has to be corrected in accordance with its deviation from the true north. Such procedures are very troublesome in practice.